Many physiological and pathological processes are known to be characterised by both a significant hyper-proliferation and mobility of cells. Among them are physiological processes like, for instance, embryogenesis or development and differentiation of tissues and, also, pathological processes among which are tumours or, more in general, disorders affecting a variety of body districts or organs: lungs, muscles, bones, skin as well as the nervous, lymphatic, gastrointestinal, renal, maculo-ocular, cardiovascular system, and the like.
In pathological or non-pathological conditions, high cellular proliferation and mobility mainly depends on the activity of zinc metalloproteases, a class of catalytic proteases present in humans (also referred to as proteinases) which are known to coordinate a zinc ion in their catalytic site, and which are able to hydrolyse amidic bonds within the peptidic chain of the proteins.
Among the zinc metalloproteases are extracellular matrix metalloproteases (hereinafter referred to as MMPs), ADAMS (A Disintegrin and Metalloproteases) and ADAMTs (A Disintegrin and Metalloprotease with Trombospondin Type I repeats).
Once produced, these proteases remain anchored onto the cellular membranes or are excreted in the extra-cellular matrix (ECM), an important physiological structure comprising an organized tri-dimensional network of cells of the surrounding tissues which are electrically, chemically and physically connected to each other.
As such, they may play a key role in several extracellular processes including cell-cell and cell-ECM interactions, as well as in physiological intracellular processes; e.g. growth, development and remodelling of tissues, transduction of intra- and inter-cellular signals and adhesion phenomena.
The proteolytic activity of these zinc metalloproteases, in physiological conditions, is highly and finely tuned by endogenous inhibitors known as tissue inhibitors of metalloproteases (TIMPs), which have been found to exert a fundamental role also in regulating the activity of ADAMs and ADAMTs.
Thus, the delicate equilibrium between MMPs and their inhibitors enables the proper functioning of all of the physiological roles in which MMPs are involved such as, for example, embryonic growth and development, tissue morphogenesis, cell migration and matrix remodelling, reproductive processes, i.e. menstrual cycle and ovulation, bone formation, adipogenesis, wound healing and angiogenesis or even release and processing of bioactive molecules as intra- or inter-cellular peptide signals.
Due to their diffusion in the human body and their exerted role, it is thus evident that any alteration in the regulation of even one of the above mentioned processes, for instance because of pathologies like tumours whose progression may determine either over-expression or under-expression of MMPs, would result, almost inevitably, in the occurrence of degenerative processes leading to an abnormal evolution and/or development of tissues.
Examples of the above pathologies in which over- or under-expression of MMPs may be involved, thus leading to an altered tissutal morphology with uncontrolled cell proliferation, may comprise: arthritis and connective tissue disorders; neurodegenerative disorders such as multiple sclerosis, Alzheimer's disease, stroke and ALS (Amyotrophic Lateral Sclerosis); cardiovascular disorders such as atherosclerosis, aneurism, heart failure, dilated cardiomyopathy; pulmonary diseases such as emphysema or cystic fibrosis; gastric ulcers; sepsis and autoimmune disorders.
In addition, during tissutal degeneration, the altered expression of these zinc proteases may also depend, for instance, from the cells type, the activation of their pro-enzymatic forms, genic transcription pathways as well as excretion and endocytosis mechanisms.
The extracellular and intracellular threshold of active zinc metalloproteases are often regulated onto the cell membrane surface by means of a catalytic shedding by other metalloproteases like the MMPs anchored onto the cellular membrane, known as Membrane-Type MMPs (MT-MMPS), by Tumor Necrosis Factor alpha convertase, better knows as TACE (and corresponding to ADAM-17), or by even other ADAMs or ADAMTs.
Therefore, for therapeutic purposes, when pathological affections occur as being characterized by a significant activity of metalloproteases on the cell surface of invasive and hyper-proliferating cells, it could be desirable to inhibit those MT-MMPs or some other ADAMs or ADAMTs.
So far, at least 23 different enzymes, which are known to belong to the family of MMPs, have been classified into sub-groups according to their substrate specificity. Among them are, as an example, MMP-1, MMP-8 and MMP-13 known to act on collagenase; MMP-2 and MMP-9, on the other side, known to target gelatinase; and MMP-3, MMP-10 and MMP-11 known to target stromelysin.
In addition, a fourth sub-group of membrane-type MMPs, called as MT-MMPs, have been identified and characterized so far, namely: MT1-MMP (MMP-14), MT2-MMP (MMP-15), MT3-MMP (MMP-16), MT4-MMP (MMP-17), MT5-MMP (MMP-24) and MT6-MMP (MMP-26); the exerted role, however, has been clarified for only some of them (see, for a reference, H G Munshi et al, Cancer Metastasis Rev., 2006, 25, 45-56; and V S Golubkov et al., J Biol. Chem., 2005, 280, 25079-25086).
As an example, MMP-14 is known to be responsible for the activation of pro-MMP-2 on the external surface of some cell types, e.g. smooth muscle cells of vascular tissue in the angiogenetic processes (see, for a reference, N. Koshikawa et al., J. Cell. Biol. 2000, 148, 615-624; and Y. Itoh, H. Nagase, Essays in Biochemistry, 2002, 38, 21-36).
In addition, MMP-14 is known to be hyper-expressed on the membranes of some types of tumoral cells, such as in melanomas (see, as a reference, NE Sounni et al., Int. J. Cancer, 2002, 98, 23-28), breast adenocarcinoma (see, as a reference, N E Sounni, et al., FASEB J 2002, 16, 555-564) and in glyomas (A T Belien, et al., J Cell Biol 1999, 144, 373-384; and E I Deryugina, et al, Cancer Res, 2002; 62:580-588).
MMP-14 may also activate other pro-MMPs like pro-MMP-13, which hyper-expression is known to be correlated, in some cell types, to tumours, inflammation or cardiovascular and neurodegenerative disorders (see, for example, A R Folgueras et al., Int. J. Dev. Biol., 2004, 48, 411-424; and J O Degushi, et al., Circulation, 2005, 2708-2715).
Even other MMPs are known to contribute to the activation of pro-MMP-2 and/or pro-MMP-13 and/or pro-MMP-9. As an example, MMP-15, MMP-16, MMP-17 and MMP-24 are known to activate pro-MMP-2 and pro-MMP-13; MMP-17 acts only to activate pro-MMP-2, whilst MMP-26 activates pro-MMP-2 and proMMP-9; see, as a reference, A R Folgueras et al., (Int. J. Dev. Biol., 2004, 48, 411-424).
Moreover, MMP-2 and MMP-13 are produced from proliferating and invasive cells and are activated, or anyway activable, in ECM by catalytic activity of the membrane surface MT-MMPs; they represent, therefore, the prior tool for cell motility across the digestive surface permeability of ECM.
Based on previous studies on the so-called “degradomics” (see, as a reference, C Lopez-Otin et al., Nature Rev. 2002, 3, 509-519; and CM Overall et al., Nature Review Cancer, 2006, 6, 227-239), the possibility of targeting some MMPs as drug delivery candidates for cancer and other pathologies, whilst avoiding interferences with physiological roles exerted by some other MMPs, is nowadays widely acknowledged.
As such, studies are ongoing for the development of MMP inhibitors, to be used in therapy, that are able to selectively address pathological affections without the aforementioned drawbacks.
Therefore, as the activity of some MMPs should be inhibited so as to limit and counteract an occurring degenerative process, the activity of some other types of MMPs regulating physiological processes of development and morphogenesis should not be impaired, as the above may result in undesirable side effects.
Among them is, as an example, the musculoskeletal syndrome with fibroproliferative effects in the join capsule of the knee known to occur upon impairment of the normal tissue remodelling activity exerted by MMP-1. Likewise, the inhibition of some MMPs involved in tumorogenesis control such as, for instance, MMP-3, may cause an increase of cellular proliferation and invasion.
In therapy, therefore, a lack of inhibition on MMP-1 and MMP-3, considered as antitarget, is highly desirable.
On the contrary, an evident selectivity toward MMP-2 and MMP-9 was found to have pro-apoptic effects on tumor cell cultures without showing important side effects.
Therefore, the search for molecules able to specifically regulate the activity of specific MMPs, when normal mechanisms are lost, will provide useful compounds for the treatment of several diseases.
A variety of metalloproteases inhibitors, some of which referring to sulphonamido derivatives, is known in the art.
Among them are, as an example, carbocyclic side chain containing N-substituted metallo protease inhibitors, described in WO 01/70720, and pharmaceutical compositions thereof.
U.S. Pat. No. 6,686,355 discloses biphenyl derivatives possessing a cyclic nitrogen containing sulphonamido group, as MMP inhibitors.
WO 2004/069365 describes diagnostic imaging agents comprising matrix metalloproteases inhibitors bearing substituted N,N-dialkyl chain sulphonamido groups, properly labelled with a γ-emitting radionuclide.
WO 98/39329 describes sulphonamido hydroxamic acid derivatives specifically targeting MMP-2, MMP-9 and MMP-13; the several compounds therein exemplified comprise substituted N,N-dialkyl side chain sulphonamido groups.
U.S. Pat. No. 7,067,670 discloses alkyl-sulphonamido hydroxamic acid derivatives possessing inhibitory activity towards MMP-2 and MMP-13.
U.S. Pat. No. 6,500,948 discloses pyridyloxy- and pyridylthio-arylsulphonamido derivatives having MMP inhibitory activity, wherein the N atom of the sulphonamido group is part of a six membered heterocycle, bearing carbon atoms adjacent to the above N atom.
U.S. Pat. No. 6,495,568 discloses alkyl- or cycloalkyl-sulphonamido hydroxamic acid derivatives as matrix metalloproteases inhibitors.
U.S. Pat. No. 5,985,900 discloses sulphonamido derivatives being characterized by a phenyl- or phenylene-SO2NH— moiety, possessing MMP inhibitory activity.
WO 99/42443 discloses sulfonylamino hydroxamic acid derivatives bearing a group aryl-SO2NH—, therein indicated as matrix-degrading metalloproteinases.
Other sulphonamido MMP inhibitors are known in the art. Among them are selective inhibitors of gelatinase A (MMP-2) being disclosed by Rossello et al. in Bioorg. & Med. Chem. 12 (2004) 2441-2450, and having formula (A) below, wherein R is a group selected from isopropyl, allyl or p-(benzyloxy)benzyl.
Likewise, MMP-2 inhibitors showing a good MMP-2/MMP-1 selectivity were also disclosed by Tuccinardi et al (Bioorg. & Med. Chem. 14 (2006) 4260-4276); among the exemplified compound therein reported is the derivative of formula (B) below

In addition to the above, previous works in this field have indicated that the use of selective MMP-2 inhibitors that spare some MMPs such as MMP-1 and MMP-3 enables to block invasion of HT1080 cells (of a highly invasive fibrosarcoma) and HUVEC (Human Umbical Vein Endothelial) cells in models of chemoinvasion and angiogenesis (A. Rossello, et al, Bioorg & Med. Chem., 2004, 12, 2441-2450; and A. Rossello, et al., Bioorg & Med. Chem. Lett., 2005, 15, 1321-1326).
As reported in the aforementioned Bioorg & Med. Chem. Lett., (2005), a possible anti-angiogenesis model was developed and specific compounds therein referred to as (5b) and (5c), which formulae are reported below, were synthesized

Based on the results being obtained on isolated enzymes and according to a method described by C G Knight et al. (see, as a reference, FEBS Lett. 1992, 296, 263; and Methods Enzymol. 1995, 248, 470), the said method comprising the use of the fluorogenic substrate FS-1 (e.g. Mca-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2) as reported by A. Rossello et al., in Bioorg. Med. Chem. Lett. 12 (2004), 2441-2450, compound (5b) proved to be a dual inhibitor of MMP-2 (IC50 value corresponding to 0.41 nM) and of MMP-14 (IC50 value corresponding to 7.7 nM).
A novel class of zinc metalloproteases inhibitors having aryl-sulphonamidic structure is deisclosed in WO 2008/113756 (PCT/EP2008/053078). Based on IC50 values of inhibition tests being in the nano/subnano molar range, those compounds resulted to be particularly effective towards target enzymes, in particular MMP-2, MMP-13 and MMP-14.
Besides of being useful in the treatment of pathological conditions the said compounds may be advantageously used, in diagnostics, when suitably labelled with imaging moieties.
In this respect, the possible visualization of body tissues, organs or districts, wherein a non-physiological overexpression of given metalloproteases occur is of utmost importance, in clinical practice, as it may represent a powerful tool for the diagnosis of pathologies associated to them, for instance including inflammatory processes leading to arthritis and connective tissue disorders, as well as degenerative processes and tumours.
In this respect, MMP inhibitors labelled with imaging moieties are already known in the art as described, for instance, in WO 01/60416, WO 2004/069365, WO 2005/049005 and WO 2006/032911.
In addition, barbiturate derivatives possessing metalloproteases inhibitory activity further labelled with fluorogenic substrates are also disclosed in Bioconjugate Chem. 2008, 19, 1001-1008.
The present invention, however, refers to diagnostic agents comprising the aforementioned class of MMP inhibitors described in WO 2008/113756, further labelled with imaging moieties known in the art.
Importantly, as the metalloproteases inhibitors therein disclosed present a remarkable inhibitory activity and, also, a high degree of selectivity towards given metalloproteases, we have found that their labelling with diagnostic imaging moieties as per the invention affords a novel class of diagnostic agents with no impairment, at least to a significant extent, of affinity against the said metalloproteases.
Hence, the compounds of the invention result to maintain a very high affinity towards specific metalloproteases and allow for an optimal diagnostic visualization of the body organs, districts or tissues wherein the non physiological overexpression of those metalloproteases may occur.
Thanks to their capability to maintain the biological profile of the parent compounds from which they derive, therefore, their administration is particularly advantageous, in clinical practice, for the visualization of body areas where the compounds may target.